Efficacy of UV irradiation on eight species of Bacillus

Ultraviolet irradiation has commonly been used in the indoor environment to eliminate or control infectious diseases such as tuberculosis in medical care facilities. Heating, ventilating, and air-conditioning (HVAC) system components such as duct-liners, cooling coils, drip-pans, interior insulation, and areas subjected to high levels of moisture can create an environment that is prone to biological contamination. Air supplied to indoor environments can carry biological contaminants that can expose numerous building occupants to pathogenic organisms. Possible terrorist activities could release biological agents into ambient air, or directly into a building environment, or HVAC system may expose multitudes of individuals to dangerous pathogens. The use of germicidal ultraviolet lamps (UVGI) in commercial and residential HVAC systems has increased. A method to determine the antimicrobial efficacy of UVGI irradiation was developed and tested on the surface of agar plates with eight varieties of Bacillus bacteria spores. Bacillus anthracis surrogates were used for their expected similar inactivation responses to UVGI irradiation. The percent kill and k value for each organism was calculated for various periods of exposure.